This project is designed to develop an improved dosage schedule for stilbestrol treatment of patients with prostatic carcinoma and to determine the mechanism for hormonal control of this neoplasm. Clinical and laboratory observations will monitor the response of tumor growth and metastasis to several dosages of stilbestrol. Measurements of plasma testosterone and luteinizing hormone levels will be used to evaluate the degree of suppression of Leydig cell function induced by stilbestrol. The product rates, interconversion and metabolic clearance rates of testosterone and androstenedione will be obtained in a group of patients prior to therapy, during stilbestrol treatment and during relapse. These observations are intended to determine the relative contribution of decreased androgen production in the therapeutic response, and to reveal an optimum dosage schedule for hormonal control of prostatic carcinoma.